1. Purpose of the Invention
This invention relates in general to certain new and useful improvements in rotary cutting devices and, more particularly, to vegetation cutting devices which employ a flexible rotating cutting element.
2. Prior Description of the Prior Art
There have been many prior art attempts to provide for a safe and efficient rotary head for rotary lawn mowers, edgers, trimmers and the like, which perform in a safe and efficient manner. In the large majority of these prior art lawn mowers, edgers and the like, the rotary or cutting element comprises a rotating metal blade or similar cutting element which is rotated at a high rate of speed to effect the cutting of grass, weeds or similar vegetation. Nevertheless, even when the device is provided with a shield around the cutting element, hazardous conditions are not completely obviated since it is possible for the user of the device to contact the high speed rotating cutting element. Moreover, these high speed rotating cutting elements may oftentimes strike rocks or similar objects in their pathway and thereby propel these objects creating a hazardous condition to property and individuals in the proximate area.
There have been various attempts to overcome these hazardous conditions which are created by the rigid type metal cutting blades in the prior art cutting assemblies. Most of these attempts to overcome the problems of the type described involve the utilization of some type of flexible flail or cord type cutting element which will have sufficient resiliency so as to overcome the problem of propelling objects which are struck by the high speed rotating cutting element. Nevertheless, these resilient type cutting elements suffer a disadvantage in that they are not safe to the operator of the device and, even more so, the mere resiliency is not sufficient to ensure that the dangerous conditions will not be created when rotation is effected at the desired cutting speeds.
Notwithstanding the above, the foregoing prior art cutting devices are so constructed that they are generally not provided with means for easy replaceability of the cutting elements in the event of wear and damage. Consequently, it is usually expensive and rather time consuming in order to replace the cutting element in these various prior art devices.
In view of the foregoing problems, there have been many proposed prior art vegetation cutting devices such as lawn mowers or trimming devices which employ a disc-like head member arranged to be rotated by an electric motor. The disc-like member contains a spool which is located within the housing in coaxially aligned relationship to the shaft of the motor. A length of flexible, non-metallic line is coiled about the spool so that its free travelling end extends generally peripherally from the spool to the lower end of the device. In this way, the free travelling end will be swung arcuately at a high speed through the actuation of the motor in order to cut adjacent vegetation in the manner of a flail.
Devices of this type have revealed that under ideal operating conditions they will trim grass or other lightweight vegetation with reasonable effectiveness. Moreover, these devices possess a significant advantage in that they are much safer to use than the more conventional cutter in that they do not discharge stones or similar objected in the manner of missiles. In this way, the devices which employ flexible cords thereby obviate the problem of stone-like missiles striking persons or property in the working area. This latter type of prior art device which employs a rotary cord-like element is also subject to certain disadvantages which similarly limit, if not destroy, its practical value. Devices of this type are effective to cut standing, lightweight vegetation, but are almost completely ineffective in other tasks, such as the cutting of heavy dense growths of vegetation. Moreover, these devices are generally only effective when cutting upright vegetation, but are not effective in cutting vegetation in a rank condition. Moreover, the cords in these prior art devices experience a breakage rate which is significantly high to effectively nullify their advantages and thereby render devices which are in many cases commercially ineffective.
Another one of the principal disadvantages of these prior art devices is that the cord, typically in the form of a filament, is not designed to replace the worn or broken cord during operation of the cutting device. Moreover, in these prior art devices, there is no provision for providing for the balance of the cord as contained upon a spool within the cutting device. In addition to the foregoing, the prior art devices contain no means to offset the tendency of the unit to be imbalanced when the cutting cord is extended to any length.